Drive pawl for electrically wound clocks



Dec. 31, 1963 R. SIEFERTO 3,115,788

DRIVE PAWL FOR ELECTRICALLY WOUND CLOCKS Filed June 27, 1962 2Sheets-Sheet 1 Dec. 31, 1963 R. SIEFERT 3,115,783

DRIVE PAWL FOR ELECTRICALLY WOUND CLOCKS Filed June 27, 1962 2Sheets-Sheet 2 United States Patent Ofiice Patented Dec. 31, 194533,115,733 DREVE ?AWL FQR ELEQTRHIALLY WGUND QLQQKd Roland Siefert,Schwenningen (Neckar), Germany, as-

signor to Kienzle Unrenfahriizen A.G., Schwenningen (Neckar), GermanyFiled .lune 27, 1962, Ser, No. 205,579 6 (Jlaims. (Cl. 74-577) Thisinvention relates to l2. drive pawl for electromagnetic wind-up devicesfor clocks or other time pieces. The drive pawl and associated ratchetwheel provide the working connection between a source of mechanicalenergy, such as a spring periodically stressed by a clapper armature,and the running works of the time piece. The hitherto usual drive pawlsare often biased with a helical torsion spring to improve engagementwith the ratchet wheel. if such a spring be strong in order to prevent ajumping out from the associated toothing there is the disadvantageduring retraction, or backward motion when the pawl rides without actionon the ratchet wheel, that the friction is very high. This leads to widevariations in winding torque, frequency of winding and consequent torqueon the works. *In order to reduce friction, weak springs are frequentlyused but they have the characteristic of rather (Li .311 allowing thepawl to spring out of Working position and consequently the time pieceis thrown out of time or put out of order.

Moreover simple leaf springs have been employed but they, too, alsoeither press too strongly so that the torque required for wind-up whenthe pawl rides backward over the teeth becomes large or the leaf springsmust be long and so lack lateral stability.

The construction of a drive pawl according to the present inventionavoids the above mentioned disadvantages. The pawl itself is a resilientarm, and so the need for a helical or coil spring is eliminated which isadvantageous both as to operation and to production costs.

In the accompanying drawing showing, by Way of example, two of manypossible embodiments of the invention,

FIG. 1 is a perspective of a winding device with parts of a :clockworks;

FIG. 2 is a plan of a drive pawl according to the invention;

FIG. 3 is a vertical sectional view of the pawl, the section being takensubstantially along the line 33 of FIG. 2 looking in the direction ofthe arrows of said line;

FIG. 4 is a plan of another form of the pawl, and

FIG. 5 is a vertical sectional view of the pawl of PEG. 4 the sectionbeing taken along the line 5-5 of HG. 4, looking in the direction of thearrows of said line.

The operation of a Wind-up device can be readily understood by referenceto FIG. 1. An electromngnet 1i periodically attracts a clapper armaturell which strikes an eccentric cylindrical pin or 12 mounted onoscillatory disc 13 of appreciable mass. The disc is mounted on a worksplate 14 for oscillation about a stub shaft so that the armature slingsor turns the disc when the crank is struck. When the disc turnsclockwise as shown in the drawing it stretches a tension spring 16attached to the plate 14 and an eccentric portion of the disc. At thesame time the drive pawl, generally designated 17, on the crank 12 ridesbackward over the ratchet wheel 18 fast on a works shaft 1). Inpractice, a stop pawl (not shown) is often used to prevent any backwardturning of the wheel, though in some constructions this is not necessaryespecially if the friction of the drive pawl is kept low. When the discreaches its limit of turning, against the tension of the spring, thedrive pawl the engages the ratchet wheel so that the spring may, through2 the pawl, drive the wheel 18 and work shaft 19 of the clockworks.

The pawl 17 is of spr'ingy strip metal having an engagement down-turnedlip portion 24 at one end near a yoke portion 21 from which extend, in agenerally opposite direction, two wide outer parallel arms 22 and anarrower tongue 23 between. The outer end portions 24 of the arms areeach cylindrically curved to embrace, side by side and coaxially,slightly more than half the circumference of the crank pin 12.

The tongue 23, between the arms and spaced laterally therefrom, isresiliently bent from the plane of the arms and resiliently engages thecrank pin on the opposite side of the axis of pin from the major portionof the curved ends so as to provide a retaining force to increase theholding of the ends around the cylindrical pin. The pawl is securedagainst undue movement of the curved ends 24 in the direction of theaxis of the pin 12 by the provision of a minor chordal slot 25 in thepin in which the tongue 23 is disposed. The tongue prevents the unduemovement by engagement against one or the other of slot side walls 27and bears resiliently against the inner edge 26 of the slot to preventan undesired flapping of the pawl or to provide bias to hold the lip 20in the teeth of the ratchet wheel id.

The pin 12 oscillates about the axis of the stub shaft 15. If the pin 12is fast on the disc, as it preferably is, the slot edge 26 turns aboutthe stub shaft, and during oscillation of the disc, the edge 26, if thestub shaft 15 and the works shaft 19 are coaxial, remains the samedistance from the periphery of the ratchet wheel 18, and the spring biason the pawl remains constant.

However, the stub and works shafts need not be exactly coaxial and sothe tension on the pawl may be made to vary according to the position ofthe disc, which will also affect the bias of the pawl due to gravity.Thus according to the combination of spring tension and weight the pawlmay have as desired a nearly constant, as well as a distorted, biasagainst the ratchet wheel depending on the positions of the disc and ofthe axis of the said shafts. Depending on the height and slope of theratchet wheel teeth it may be desirable to have the pawl bias againstthe wheel stronger, say, when the disc approaches run-down position.

By a system of gears (not shown), the pin 12 may turn relative to thedisc, as the latter turns about the stub shaft, and so vary the springtension on the pawl according to the position of the disc.

in another form of the pawl as shown as 17a in FIGS. 4 and 5 the arms 22of FIGS. 3 and 4 are replaced by side flanges 22a at right angles to theplane of the yoke portion 21. The outer end portions of the flanges areprovided with alined bearing holes 28 receiving the pin 12. In this formof the invention the tongue disposed in the slot overlies the pin and ison the outer edge 26a of the slot to cause the pawl to bear against theratchet wheel. The pawl 17:; may be made quite rugged by the provisionof a diamond shaped dimple 2% at the line of junction between the lipand yoke portion and by a weblike tie piece 3t? between the sideflanges.

In either form of the invention the tongue may be sprung temporarily topermit the sliding of the pawl onto the pin 12 longitudinal thereof toregister the tongue and slot, and then the tongue is allowed to engagethe appropriate edge of the slot in order to cause the pawl to bearagainst the ratchet wheel. The slot walls prevent the tongue and pawl asa whole from unduly moving laterally.

The invention claimed is:

l. A drive pawl combination for an oscillatory windup device of anelectromagnetically wound time piece, characterized by the inclusion ofan oscillatory ineitia memher, a crank pin on the member, said pinhaving a chordal slot therein, a pawl mounted on the pin for turningslightly thereon and having a resilient tongue in the slot for tendingto turn the pawl about the pin, the tongue being engageable with theside walls of the slot to limit lateral movement of the pawl, and aratchet wheel engage able with the pawl.

2. In an electrically wound clock, an inertia member mounted for turningand a cylindrical crank pin thereon, the pin having a chordal slottherein, an elongated pawl having a yoke and lip portion at one endportion for engagement with a ratchet wheel and substantially monoplanararms terminating at the other end as slightly more than semicylindn'calclaws partially embracing the pin on each side of the slot as bearingsfor the pawl, a resilient tongue fast on the yoke portion and in theslot and tensed against an edge of the slot parallel with the axis ofthe pin for tending to turn the pawl and claws about the pin, saidtongue being adapted to engage the side walls of the slot to preventlateral movement of the pawl on the pin, and a ratchet wheel for thepawl to engage on.

3. In an electrically wound clock, an inertia member mounted for turningand a cylindrical crank pin thereon,

the pin having a chordal slot therein, two like substantially parallelarms of strip material each having alined bearing openings at one oftheir end portions and receiving the pin, a yoke portion connecting thetwo arms at their other end portion, and a lip portion adapted to engagea ratchet wheel and integral with the yoke portion, a resilient tonguefast on the yoke portion and between the arms and tensed against the pinand lying in the slot, for tending to turn the arms about the pin andlimiting motion of the arms in a direction axially along the slot.

4. In a clock as claimed in claim 3 said tongue bearing on an edge ofthe slot parallel with the axis of the pin.

5. in a clock as claimed in claim 4, said arms lying in substantially asingle plane to which the axis of the pin is parallel.

6. In a clock as claimed in \claim 4 said arms lying in diiierent planesto which the axis of the pin is substantially perpendicular.

Tratsch Jan. 11, 1949 Watson May 9, 1961

1. A DRIVE PAWL COMBINATION FOR AN OSCILLATORY WINDUP DEVICE OF AN ELECTROMAGNETICALLY WOUND TIME PIECE, CHARACTERIZED BY THE INCLUSION OF AN OSCILLATORY INERTIA MEMBER, A CRANK PIN ON THE MEMBER, SAID PIN HAVING A CHORDAL SLOT THEREIN, A PAWL MOUNTED ON THE PIN FOR TURNING SLIGHTLY THEREON AND HAVING A RESILIENT TONGUE IN THE SLOT FOR TENDING TO TURN THE PAWL ABOUT THE PIN, THE TONGUE BEING ENGAGEABLE WITH THE SIDE WALLS OF THE SLOT TO LIMIT LATERAL MOVEMENT OF THE PAWL, AND A RATCHET WHEEL ENGAGEABLE WITH THE PAWL. 